His interest in painting was initiated by his father, the painter Alfredo Souto, although he was forced to study for obtaining the Quantity Surveyor degree, which he will leave soon to enter the Academy of Fine Arts of San Fernando in Madrid.
Souto participates in the National Exhibitions of Fine Arts and in 1925 exhibits his works in the House of Galicia in Madrid. The next year he goes to Paris until 1928, where he realizes some works related with impressionism, cubism and expressionism. In 1931, he signs the AGAP (The Professional Association of Plastic Artists) together with Santiago Almela, Francesc Badía, Emiliano Barral, Botí, Julián Castedo, Climent, Rafael Dieste, Isaías Díaz, Díaz Yepes, Cristino Mallo, Mateos, Francisco Maura, Moreno Villa, Santiago Pelegrín, Pérez Mateo, Servando del Pilar, José Planes, Puyol, Renau, Rodríguez Luna, Santa Cruz and Winthuysen.
The thirties are characterized by his numerous expositions: Ateneo (1930-1933), Lyceum Female Club (1930), Circle of Fine Arts (1932), Association of Basque Artists from Bilbao (1932), Vigo´s Casino (1933), Society of Iberian Artists in San Sebastián (1931), Copenhague (1932), Berlin (1933) and Paris (1936), etc.
He was an active main character of the Spanish art in the first half of the XX century; it is interesting to see how, within the limits of figurative art, he was always between the best ones.
In 1934 he is granted to attend the Spanish Academy in Rome where he is influenced by the metaphysical painting and the members of the Novecento group. Classicist Architecture, space strangeness, archaic aesthetics and the rough aspect of the mural painting are features found in his works at this stage.
After the outbreak of the civil war, he goes to Valencia, where he collaborates with the republican propaganda. In 1937 he displays in the republican stand in the Paris Exhibition. Later, as exiled, he starts travelling between Paris, Belgium, New York, Havana, Mexico etc. In the American continent he gets a chance to free his art of some imposed conventions, above all, the naturalism, starting a stage specially focused in the autonomous study of colour.